From e06528c64b62abbaa49dedc395e1ce58ad3962fe Mon Sep 17 00:00:00 2001
From: "R. David Murray" <rdmurray@bitdance.com>
Date: Tue, 3 Aug 2010 23:35:44 +0000
Subject: Merged revisions 83690 via svnmerge from
 svn+ssh://pythondev@svn.python.org/python/branches/py3k

........
  r83690 | r.david.murray | 2010-08-03 18:14:10 -0400 (Tue, 03 Aug 2010) | 10 lines

  #3196: if needed pad a short base64 encoded word before trying to decode.

  The RFCs encourage following Postel's law: be liberal in what you accept.
  So if someone forgot to pad the base64 encoded word payload to an
  even four bytes, we add the padding before handing it to base64mime.decode.
  Previously, missing padding resulted in a HeaderParseError.

  Patch by Jason Williams.
........
---
 Lib/email/header.py          |  3 +++
 Lib/email/test/test_email.py | 11 ++++++++++-
 Misc/ACKS                    |  1 +
 Misc/NEWS                    |  3 +++
 4 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/Lib/email/header.py b/Lib/email/header.py
index 3215a80..afcea40 100644
--- a/Lib/email/header.py
+++ b/Lib/email/header.py
@@ -94,6 +94,9 @@ def decode_header(header):
             word = email.quoprimime.header_decode(encoded_string)
             decoded_words.append((word, charset))
         elif encoding == 'b':
+            paderr = len(encoded_string) % 4   # Postel's law: add missing padding
+            if paderr:
+                encoded_string += '==='[:4 - paderr]
             try:
                 word = email.base64mime.decode(encoded_string)
             except binascii.Error:
diff --git a/Lib/email/test/test_email.py b/Lib/email/test/test_email.py
index 7d91d25..0559142 100644
--- a/Lib/email/test/test_email.py
+++ b/Lib/email/test/test_email.py
@@ -1645,6 +1645,15 @@ Re: =?mac-iceland?q?r=8Aksm=9Arg=8Cs?= baz foo bar =?mac-iceland?q?r=8Aksm?=
                               (b'rg', None), (b'\xe5', 'iso-8859-1'),
                               (b'sbord', None)])
 
+    def test_rfc2047_B_bad_padding(self):
+        s = '=?iso-8859-1?B?%s?='
+        data = [                                # only test complete bytes
+            ('dm==', b'v'), ('dm=', b'v'), ('dm', b'v'),
+            ('dmk=', b'vi'), ('dmk', b'vi')
+          ]
+        for q, a in data:
+            dh = decode_header(s % q)
+            self.assertEqual(dh, [(a, 'iso-8859-1')])
 
 
 # Test the MIMEMessage class
@@ -3172,7 +3181,7 @@ A very long line that must get split to something other than at the
 
     def test_broken_base64_header(self):
         raises = self.assertRaises
-        s = 'Subject: =?EUC-KR?B?CSixpLDtKSC/7Liuvsax4iC6uLmwMcijIKHaILzSwd/H0SC8+LCjwLsgv7W/+Mj3IQ?='
+        s = 'Subject: =?EUC-KR?B?CSixpLDtKSC/7Liuvsax4iC6uLmwMcijIKHaILzSwd/H0SC8+LCjwLsgv7W/+Mj3I ?='
         raises(errors.HeaderParseError, decode_header, s)
 
 
diff --git a/Misc/ACKS b/Misc/ACKS
index 03f96eb..6486e79 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -817,6 +817,7 @@ Felix Wiemann
 Gerry Wiener
 Frank Wierzbicki
 Bryce "Zooko" Wilcox-O'Hearn
+Jason Williams
 John Williams
 Sue Williams
 Gerald S. Williams
diff --git a/Misc/NEWS b/Misc/NEWS
index 8e164a9..262bd5e 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -84,6 +84,9 @@ C-API
 Library
 -------
 
+- Issue #3196: email header decoding is now forgiving if an RFC2047
+  encoded word encoded in base64 is lacking padding.
+
 - Issue #8447: Make distutils.sysconfig follow symlinks in the path to
   the interpreter executable.  This fixes a failure of test_httpservers
   on OS X.
-- 
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